As Pleurotus spp. native in Japan (hereinafter referred to as domestic varieties), P. ostreatus (Jacq.: Fr.) Kummer (SEQ ID NO. 1), P. salmoneostramineus L. Vass., P. cornucopiae (Paulet) Rolland var. citrinopileatus (Sing.) Ohira, P. abalonus Y. H. Han, K. M. Chen & S. Cheng and P. pulmonarius (Fr.) Quel., etc. have conventionally been known. Among these, P. ostreatus (Jacq.: Fr.) Kummer has been enjoyed as a minor forest product, but the disadvantage is that caps are liable to be broken in the course of distribution and cooking, and therefore the amount of domestic production has been decreasing since about 1989.
On the other hand, as Pleurotus spp. that are not native in Japan (hereinafter referred to as foreign varieties), P. eryngii (DC.:Fr.) Quel. (SEQ ID NO. 3), P. nebrodensis (DC.:Fr.) Quel. (SEQ ID NO. 2), P. eryngii (DC.:Fr.) Quel. var. ferulae Lanzi, P. eryngii (DC.:Fr.) Quel. var. elaeoselini (SEQ ID NO. 4), P. eryngii (DC.:Fr.) Quel. var. tuoliensis C. J. Mou, etc. have been known (Non-Patent Literature 1, Non-Patent Literature 2), and P. eryngii (DC.:Fr.) Quel. have been produced and sold in Japan since about 1995, and P. eryngii (DC.:Fr.) Quel. var. tuoliensis C. J. Mou, etc. also came to be sold several years later. Among these, P. eryngii (DC.:Fr.) Quel. is a high-demand commodity, and the amount of domestic production has been increasing. P. eryngii (DC.:Fr.) Quel. var. tuoliensis C. J. Mou, etc. that got into the business later have not expanded the market yet as a new market because, among others, they are similar to P. eryngii (DC.:Fr.) Quel., and therefore there is a strong need to develop novel varieties.
Incidentally, in the Pleurotus spp., the crossbreeding among foreign varieties has recently been confirmed (Non-Patent Literature 2). However, there is no example of crossbreeding a domestic variety with a foreign variety, and in regard of the genealogical tree, it is believed that those species cannot be crossbred because they can be classified into different groups (Non-Patent Literature 2, Non-Patent Literature 3). Accordingly, no novel species having both characteristics of a domestic variety and a foreign variety has been developed yet (Patent Literatures 1-6).